Quad processor

ABSTRACT

The present invention includes plural plasma etching vessels and a wafer queuing station arrayed with a wafer transfer arm in a controlled environment. Wafer processing in each vessel is regulated by a state controller for processing a plurality of wafers from a single cassette, contained within the vacuum environment of the plural plasma etching vessels and wafer queuing station, to provide an orderly and efficient throughput of wafers for diverse or similar processing in the plural vessels. In this manner a wafer can be processed as soon as a vessel becomes available.

FIELD OF THE INVENTION

This invention is directed to the field os semiconductor processing, andmore particularly, to a novel multiple-processing and contamination-freeplasma etching system.

The present invention represents an extension of our patent applicationSer. No. 853,775 filed Apr. 18, 1986 with the same assignee.

BACKGROUND OF THE INVENTION

Plasma etching devices are commonly employed during one or more of thephases of the integrated circuit fabrication process, and are typicallyavailable in either a single-wafer or a plural-wafer configuration. Thesingle-wafer configurations, while providing excellent process control,suffer from a restricted system throughput capability. Efforts torelieve the throughput limitations, have been generally unsuccessful.For these high-temperature etching processes, system utility is limiteddue to the undesirable phenomenon of resist "popping", notwithstandingthat various cooling approaches have been used including clamping,cooling of the wafer underside with a helium flow, and the mixing ofhelium into the plasma. The multiple-wafer configurations, whileproviding a comparatively much-greater system throughput, have beengenerally subject to less-than-desirable process and quality control.Not only are end-point determinations for each of the multiple waferseigher not available or not precisely determinable, but also electrodepositional accuracy for different electrode gaps and correspondinglydifferent gas chemistries is often difficult to establish and maintain.The single-wafer and the multiple-wafer configurations are both subjectto the further disadvantage that two or more step processes typicallyexpose the wafers to an undesirable environment in the intermediatehandling step, which materially increases the possibility of wafercontamination, and which further restricts the processing throughput.

SUMMARY OF THE INVENTION

The present invention contemplates plural single-wafer plasma reactorseach operative individually to provide excellent process control ofsingle wafers, collectively operative to provide a system throughputlimited only by the number of the plural plasma reactors, and socooperative with a common wafer transfer and queuing means as to provideboth single-step and multiple-step wafer processing in a manner thatneither exposes the wafers to an undesirable atmosphere not to humanhandling.

In the preferred embodiment, plural plasma reactors and cassetteelevator are symmetrically arrayed about an X, TT movable waver armassembly. The plural reactors, the cassette elevator, and the X, TTmovable wafer arm are maintained in a controlled vacuum condition, andthe central S, TT movable wafer arm is in radial communication with theperipherally surrounding plasma reactors and cassette elevator via acorresponding one of a plurality of vacuum lock valves. The arm of theR, TT movable wafer arm assembly includes an apertured platform forsupporting each wafer, and a cooperative bumper for releasably engagingthe back and the periphery of the supported wafer without any waferfront surface contact. Plural wafer contact responsive sensors mountedto the platform are operative to provide a signal indication of whetheror not the wafer is in a properly seated condition. Each of the pluralplasma reactors includes a stationary bottom electrode and a movableupper electrode that are cooperative to provide a variable wafer-cathodeto anode gap therebetween of a selectable dimension. In one embodiment,a support assembly including a micrometer adjustment stop is providedfor selectively positioning the movable electrode, and in anotherembodiment, a combination micrometer stop and pneumatic actuators areprovided for selectively positioning the movable electrode. A verticallymovable pedestal is slidably mounted centrally to the stationaryelectrode of each of the plural plasma reactors that cooperates with theapertured platform of the R, TT movable wafer arm assembly to load andunload the wafers respectively onto and off of the stationary electrode.A reactant gas injection system, a RF power source, and an end-pointdetermination means are operatively coupled to each of the plural plasmareactors. The plural plasma reactors are operable in either embodimentto run the same or different processes, and are cooperative with the R,TT movable wafer arm assembly to provide one of the same single-stepprocessing simultaneously in the plural plasma reactors, differentsingle-step processing simultaneously in the plural plasma reactors, andsequential two or more step processing in the plural reactors. Twoembodiments of the R, TT movable wafer arm assembly are disclosed.

DETAILED DESCRIPTION OF THE DRAWINGS

These are other features, and advantages, of the present invention willbecome apparent as the invention becomes better understood by referringto the following solely-exemplary and non-limiting detailed descriptionof the preferred embodiments thereof, and to the drawings, wherein:

FIG. 1 is a pictorial diagram illustrating the multiple-processing andcontamination-free plasma etching system according to the presentinvention;

FIG. 2 is a fragmentary plan view, partially broken away, of themultiple-processing and contamination-free plasma etching systemaccording to the present invention;

FIG. 3 illustrates in FIG. 3A and in FIG. 3B partially schematic sideand end elevational views respectively illustrating the vacuum locksintermediate a corresponding plasma reactor and the R, TT movable armassembly of the multiple-processing and contamination-free plasmaetching sytem according to the present invention;

FIG. 4 is a partially pictorial and partially sectional view useful inexplaining the operation of the R, TT movable wafer arm assembly of themultiple-processing and contamination-free plasma etching systemaccording to the present invention;

FIG. 5 is a perspective view of a first embodiment of R, TT movablewafer arm assembly of the multiple-processing and contamination-freeplasma etching system according to the present invention;

FIGS. 6 and 7 are plan views of the first embodiment of the R, TTmovable wafer arm assembly illustrating different movement positions ofthe R, TT movable wafer arm assembly of the multiple-processing andcontamination-free plasma etching system of the present invention;

FIG. 8 is a partially broken-away and fragmentary isometric viewillustrating a portion of the first embodiment of the R, TT movable armassembly of the multiple-processing and contamination-free plasmaetching system of the present invention;

FIG. 9 is a partially pictorial and partially schematic side viewillustrating a plasma reactor of the multiple-processing andcontamination-free plasma etching system according to the presentinvention;

FIG. 10 is a diagramatic view illustrating the several reactantinjection systems and controlled vacuum system of themultiple-processing and contamination-free plasma etching system of thepresent invention;

FIG. 11A is a perspective view and FIG. 11B is a sectional view of asecond embodiment of the R, TT movable arm assembly of themultiple-processing and contamination-free plasma etching system of thepresent invention;

FIG. 12 is a perspective view of a portion of the second embodiment ofthe R, TT movable wafer arm assembly of the multiple-processing andcontamination-free plasma etching system according to the presentinvention; and

FIGS. 13-18 are SEM micrographs illustrating exemplary microstructuresobtainable by the multiple-processing and contamination-free plasmaetching system according to the present invention.

FIG. 19 is a system level state diagram describing system initializationand cassette insertion and extraction states;

FIG. 20 is a state diagram identifying states associated with systemprocessing of wafers and individual wafer processing instructions;

FIG. 21 is a state diagram identifying states in sequencing a wafer fromone plasma etch vessel or chanber to another;

FIG. 22 is a state diagram identifying wafer transport from a vessel orchamber to its cassette slot;

FIG. 23 is a state diagram identifying wafer transport from a cassetteslot to a vessel or chamber;

FIG. 24 is a state diagram identifying the wafer processing within anindividual plasma etch vessel or chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, generally designated at 10 is a pictorialdiagram illustrating the multiple-processing and contamination-freeplasma etching system according to the present invention. The system 10includes a plurality of single-wafer plasma reactors generallydesignated 12 to be described and a wafer queuing station generallydesignated 14 to be described that are arrayed about a closed locus asillustrated by a dashed line 16. A load/unload module generallydesignated 18 to be described is disposed concentrically within theplural plasma reactors 12 and the queuing station 14 for singlytransferring wafers to be processed and after processing between thequeuing station 14 and one or more of the plasma reactors 12. Aplurality of vacuum locks generally designated 20 to be described areindividually provided at the interfaces of the several plasma reactors12 and the load and unload module 18, and between the interface of thequeuing station 14 and the load and unload module 18. A processor 22 isoperatively coupled to the plural plasma reactors 12, to the queuingstation 14, and to the load and unload module 18 for activating andde-energizing radio frequency plasma inducing fields in well-knownmanner, for controlling and processing in well-knwon manner the signaloutput of end-point determination means coupled to the several plasmareactors, and for initiating and coordinating wafer transfer between theseveral reactors and the queuing station to be described.

A reactant gas injection system 24 to be described is operativelycoupled to the plural plasma reactors 12 for controllably injectingpreselected reactants and other process gases severally into the pluralplasma reactors. A vacuum system 26 is operatively coupled to thereactors 12, to the queuing station 14, and to the load and unloadmodule 18 for maintaining the entire assembly at a controlled vacuumcondition during operation. The process 22 is operatively coupled to thereactant gas injection system and to the vacuum system 26.

The several reactors 12, the queuing station 14, and the concentric loadand unload module 18 conserve space utilization and in much a way as toprovide a comparitively-compact plasma etching system. The load andunload module 18 and cooperative ones of the vacuum locks 20 areoperable to transfer wafers singly between the queuing station 14 andselected reactors 12 in a single-step processing mode and betweenselected reactors 12 in a two or more step processing mode without anyresidual or environmentally-induced wafer contamination as well aswithout intermediate operator handling. Among other additionaladvantages, the plasma etching system of the present invention ischaracterized by both an excellent process control and a high processingthroughput, the mutual coexistence of both features having notheretofore been possible in a practicable embodiment.

Referring now to FIG. 2, generally designated at 30 is a fragmentaryplan view, partially broken-away, illustrating the multiple-processingand contamination-free plasma etching system of the present invention.The queuing station 14 preferably includes a cassette, not shown, havingplural vertically-spaced wafers 32 stacked therein. The cassette ispreferably mounted for vertical stepping motion by an indexed elevatorassembly schematically illustrated at 34, that is operable under controlof the processor 22 (FIG. 1) to step the cassette in vertical incrementsthat correspond to the spacing of the vertically spaced wafers foraddressing the associated cassette slot position. It will be appreciatedthat in this way individual wafers in the cassette are addressed forremoval for processing and for return after processing to theircorresponding slot positions. It should be noted that although acassette and indexed elevator assembly are presently preferred, anyother suitable wafer queuing station can be employed as well withoutdeparting from the inventive concept.

Referring now to FIGS. 2, 3A and 3B, the vacuum locks 20 intermediatethe queuing station 14 and the load/unload module 18 and intermediatethe plural plasma reactors 12 and the load and unload station 18 eachinclude a housing body generally designated 40. The housing 40 includesa plate 42 having opposing top, bottom, and side walls 44 orthogonalthereto that cooperate to define a generally-rectangular hollowgenerally designated 46 therewithin as best seen in FIG. 3A. A flange 47is provided peripherally around the walls 44 on the ends thereof remotefrom the plate 42, and bolts 48 are provided through the ends of theplate 42 and of the flange 47 for fastening the housing body 40 at theinterfaces between corresponding ones of the plasma reactors 12 and theload and unload station 18 and between the interface between the queuingstation 14 and the load and unload station 18. O-rings 50 are providedon the sealing faces of the plate 42 and flange 47 for providing anair-tight seal. An elongated slot generally designated 54 is providedthrough the plate 47 that is in communication with thegenerally-rectangular hollow 46.

A chamber door assembly generally designated 56 is cooperative with theslot 54 to provide a valving action. The door assembly 56 includes anelongated, generally-rectangular plate 58 of dimensions selected to belarger than the dimensions of the slot 54. An O-ring sealing member 60is provided in the sealing face of the plate 58 and surrounding the slot54. The plate 58 is fastened to an arm 62 that is mounted for rotarymotion with a shaft 64 journaled in spaced bearings 66 that are fastenedto the plate 42. A chamber door TT-drive actuator, not shown, isfastened by the shaft 64 through and edge of the housing 40 preferablyvia a ferrofluidic or other rotary seal as illustrated dashed at 70.

The chamber door 56 is pivoted by the chamber door TT-drive actuatorbetween an open condition, illustrated in dashed outline in FIG. 3A, anda closed condition, illustrated in solid outline in FIGS. 3A and 3B. Inits open condition, the generally rectangular hollow 46 is in opencommunication with the elongated slot 54, so that a wafer arm assemblyto be described may readily be moved therethrough between the load andunload station 18 and the several plasma reactors 12 and the queuingstation 14. In the closed condition of the door assembly 56, the loadand unload module is sealed from the plural plasma reactors 12 and fromthe queuing station 18.

Referring now to FIGS. 2 and 4, the load and unload module 18 includes atop wall 72, pentagonally-arranged side walls 74, and a pentagonalbottom wall 76 defining an enclosure generally designated 78. A R, TTmovable wafer arm assembly generally designated 80 to be described ismounted in the enclosure 78. The assembly 80 includes a turntable 82mounted for TT-rotation with a shaft 84 journaled in a bearing assemblygenerally designated 86 that is fastened in a central aperture providedtherefor in the bottom wall 76. A Theta drive motor 88 mounted to thebottom wall 76 is operatively coupled to the shaft 84 via a belt andwheel arrangement generally designated 90. With controlled rotation ofthe shaft of the Theta-motor 88, the shaft 84 and therewith theturntable 82 rotates to any selected angular TT orientation for aligningthe wafer arm assembly 80 with any one of the plasma reactors 12 or withthe queuing station 14 at the corresponding TT₁, TT₂, TT₃, TT₄, TT₅coordinates.

A shaft 92 is concentrically mounted within the shaft 84 and journaledfor rotation therein on a bearing and vacuum seal assembly generallydesignated 93. Any suitable rotary vacuum seal, such as a ferrofluidicrotary vacuum seal, may be employed. On end of the shaft 92 is connectedto pivot bearing 94 to be described vacuum-mounted through the turntable82, and the other end of the shaft 92 is operatively coupled to aR-drive motor 96 via a belt and wheel arrangement generally designated98. As described more fully below, with the controlled rotation of theshaft of the R-drive motor 96, the wafer arm of both embodiments of theR, TT movable wafer arm assembly to be described is controllablytranslated in the R-direction for loading and unloading individualwafers into and out of the plural reaction chambers 12 and queuingstation 14 through the associated vacuum lock 20.

Referring now to FIGS. 2, 4, and 5, the wafer arm assembly 80 includes awafer receiving and releasing paddle assembly generally designated 100.The paddle assembly 100 includes a platform 102 having a central openinggenerally designated 104 therethrough. The member 102 terminated inlaterally spaced fingers 106 having wafer-periphery engaging upstandingflanges 108 integrally formed on the free ends thereof. A releasableabutment generally designated 110 having a bumper portion 112 and anintegral tail portion 114 is mounted for sliding motion to the platformmember 102. As best seen in FIG. 8, a coil spring 116 is mounted betweenthe releasable abutment 110 and the member 102 which urges the bumper112 in the direction of an arrow 118 so as to abut and therewithfrictionally engage the periphery of a wafer, not shown, receivedbetween the bumper 112 and the flanges 108. The tail 114 includes adownwardly depending stop 120 to be described that is slidably receivedin an elongated aperture provided therefor in the platform member 102that is cooperative with an upstanding abutment to be described torelease the frictional wafer engagement as the arm reaches its positionof maximum extension. The paddle assembly 100 is mounted between plates124 to a carriage assembly generally designated 126 that is slidablemounted on linear bearings 128 that are fastened to end posts 130upstanding from and fastened to the rotatable turntable 82.

The carriage 126 is controllably moved in either direction along thelinear bearings 128 for loading and unloading wafers individually to andfrom the several plasma reactors 12 and the queuing station 18. A member131 is pivotally mounted subjacent the carriage 126, which housestherein a linear bearing, not shown. A shaft 132 is slidably receivedthrough the linear bearing of the pivoting housing 131. One end of theshaft 132 is slidably mounted in a sleeve 134 that is mounted for rotarymotion to the turntable 82 via a pivot bearing 136, and the other end ofthe shaft 132 is fastened to a needle bearing assembly 138 that ispivotally fastened to a crank arm 140 mounted for rotation with theshaft 92 of the R-drive motor 96 (FIG. 4) via a mounting coupling 142fastened to the turntable 82.

With controlled rotation of the Theta-drive 88, the turntable 82 andtherewith the paddle assembly 100 is rotated to that TT coordinate thatcorresponds to any selected one of the angular locations of the pluralplasma reaction chambers designated TT1 through TT4 in FIG. 2, and tothat TT coordinate that corresponds to the angular location of the waferqueuing section 14 designated TT5 in FIG. 2. With the controlledrotation of the R-drive motor 96, the crank 140 traces an arcuate pathas illustrated by an arrow 144. The arm 132 therewith pivots on thepivot bearing 136 as shown by an arrow 146, and moves the carriage 126linearly along the bearings 128 in a direction that corresponds to thesense of rotation of the X-drive motor as illustrated by an arrow 148.The arm is either more or less elongated relative to the coupling 136 asit is pivoted by the crank 140, and depending on the sense of therotation, it slides within the sleeve 134 and within the housing 131 asillustrated by an arrow 150. When the crank 140 is turned to its maximumclockwise position, the paddle assembly 100 moves into its fullyretracted position as illustrated generally at 152 in FIG. 6. Withcounterclockwise motion of the crank arm 140 the paddle moves along theR direction as illustrated generally at 154 in FIG. 7. As the paddleassembly 100 nears its fully extended position, close to the maximumallowed counterclockwise rotation of the R-drive motor, the stop 120 onthe tail portion 110 abuts the confronting wall of the upstanding endpost 130, such that with continued motion of the paddle along the Rdirection the bumper 110 draws away from the flanges 108 and therebyreleases the frictional engagement of the wafer periphery. In themaximum extended position, then, the wafers are free to be loaded orunloaded to and from any selected plasma reactor 12 and/or are free forpick up or delivery back into the queuing station 14.

Contacts 156, preferably three in number, are mounted to the platformmember 102 of the paddle assembly 100 as shown in FIG. 7. The contactsare operative in response to the presence of a supported wafer toprovide a three-point signal indicative of whether or not the wafer isproperly seated on the wafer transfer arm. The contacts preferably areformed on a printed circuit board, not shown, mounted to the paddleassembly 100. A different number thereof, or other sensing means may beutilized, so long as an accurate indication of intended seating ofindividual wafers is provided.

Referring now to FIG. 9, generally designated at 160 is a partiallypictorial and partially schematic side view illustrating a plasmareactor of the multiple-processing and contamination-free plasma etchingsystem according to the present invention. Each of the plasma reactors160 includes a top plate 162, a spaced-apart bottom plate 164 and acylindrical sidewall 166 cooperate to define a plasma chamber generallydesignated 168. A first electrode generally designated 170 is fastenedto the bottom plate 164. A pedestal schematically illustrated dashed at172 is slidably mounted centrally in the bottom electrode 170 forvertical motion with the shaft of a pneumatic cylinder schematicallyillustrated in dashed outline 174. As described more fully below, thepedestal 172 is cooperative with the paddle arm assembly to allow forremoval and delivery of individual wafers into and out of the plasmachambers. The pedestal pneumatic cylinder 174 is driven by a controlledair supply, not shown, operatively coupled thereto via an air input port176 and an air output port 178. As illustrated by dashed outline 180, asource of colling liquid, not shown, is coupled to internal fluid flowpassageways, not shown, provided through the interior of the bottomelectrode 170 via input and output ports 182, 184 for removing the heatproduced in the bottom electrode during plasma etching. A top electrodegenerally designated 186 is fastened to a support shaft generallydesignated 188 that is slidably received through the top plate 162 in avacuum-tight sealing engagement therewith as by a stainless steel vacuumbellows 190 fastened between the top plate 162 and a superadjacent shaftsupport plate 187. The top electrode 186 includes internalcooling/heating fluid flow passageways schematically illustrated indashed outline 189 that are coupled via fluid flows conduits 190disposed in the shaft 188 to a source, not shown, via a liquid inputport 194 and an output port 196 provided in the plate assembly 187. Apneumatic actuator generally designated 200 having a ram 202 is mountedto the support plate assembly 187. With the ram 202 in its extendedposition, not shown, the plate 187 moves upwardly, and therewith theshaft 188 and electrode 186 move upwardly and away from the stationarybottom electrode 170. With the ram lowered as shown, micrometeradjustment posts 204 fastened to the plate assembly 187 bear against thetop plate 162 and therewith support the top electrode 186 in an intendedspaced-apart relation with the bottom electrode 170. The gap between theelectrodes is adjustable by changing the length of the micrometeradjustment posts selectively. In the preferred embodiment, between 2/16inch to 2 inches of gap adjustment is provided.

The shaft 188 has a hollow interior generally designated 206, and alaser window 208 is mounted across the hollow of the shaft 206. The beamof an external laser, not shown, passes through the window and hollowshaft for providing end-point determinations of the plasma etch state.Other end-point determination means, such as a lateral optical detector,may be employed as well without departing from the inventive concept.Reactant gas injection ports 210 are coupled via internal shaft conduitsprovided therefor, not shown, to a liquid-cooled showerhead gas manifoldillustrated in dashed outline 211 in the upper electrode 186. Reactantgas is controllably released therefrom into the plasma reactor, andradio frequency power is applied in the plasma reaction chambers. In analternative embodiment, the spacing between the electrodes can bepreselected for each particular plasma process, and additionalmicrometers, in place of the pneumatic actuators 200, can advantageouslybe employed.

Referring now to FIG. 10, generally designated at 212 is a schematicdiagram illustrating the presently preferred gas injection andcontrolled vacuum systems. Preferably, four independently valved sourcesof gases are respectively connected to individual ones of plasma vesselsvia corresponding ones of a plurality of gas manifolds, two banks of gassources generally designated 214, 216 and two manifolds 218, 220 beingspecifically illustrated. A vacuum system 222 is operatively coupled incommon to the plural plasma reactor chambers, to the queuing station224, and to the load and unload island 226. The vacuum system controlsthe vacuum condition in the entire system, so that the wafers are freefrom possible contamination as the vacuum locks are severally opened andclosed during single and multiple phase processing wafer transfer. Itshould be noted that while four plasma reactors are disclosed, a greateror a lesser number can be employed without departing from the inventiveconcept.

Referring now to FIG. 11A, generally designated at 230 is a perspectiveview of an alternative embodiment of the X. TT wafer arm assemblyaccording to the present invention. The assembly 230 includes a pully232 mounted for rotation with the shaft of the TT drive motor as bestseen in FIG. 11B. The pulley 232 includes a grooved rim 234 around whicha cable 236 is wrapped. The cable is drawn tangentally to the groovedrib 234 in opposing directions, and respectively wrapped over pulleys238, 240 and tied to a slide 242, as best seen at 244 in FIG. 11B. Withthe angular rotation of the pulley 232, the slide 242 linearly movesalong the linear bearings 246. A wafer arm generally designated 248 ismounted for movement with the slide 242 such that the arm 248 iscontrollably extended and retracted in dependence on the angularposition of the pulley 232. To provide constant-tension in the cable236, the ends of the cable preferably are terminated in the slide 242against resilient biasing elements generally designated 250 in FIG. 12.The cable 236 as it stretches is pulled in a reverse direction by theresilient couplings 250 for maintaining its intended state.

During the plasma chamber load cycles, the Theta-drive motor turns theturntable of the R, TT wafer arm assembly to the TT coordinate of thequeuing station in either embodiment of the R, TT movable wafer armassembly. The vacuum lock of the associated interface is released, andthe arm is extended under the wafer in the addressed cassette slotposition. The arm is then retracted back into the load and unloadmodule, and the vacuum lock is restored. The R, TT wafer arm assembly isthen rotated to the TT coordinate of the selected plasma reactor. Theassociated chamber door is then rotated to its open condition forproviding access to the selected reaction chamber, and the upperelectrode is raised. The wafer receiving arm is then extended in the Rdirection through the associated slot valve opening and into theselected reaction chamber. As it approaches the limit of its maximumradial travel, the depending stop flange on the wafer arm abuts theupstanding end post on the turntable and, with continued radial motion,the bumper withdraws thereby freeing the wafer from peripheral frictionengagement. The central pedestal of the lower electrode is thencontrollably raised by its pneumatic actuator, and therewith the wafersupported on the arm is elevated upwardly off of the wafer supportplatform. Thereafter, the wafer arm is retracted out of the plasmachamber through the open slot valve and back into the load and unloadstation. The pedestal is then controllably lowered. The wafer lowerstherewith until the pedestal is in its retracted position and the waferis supported on the surface of the lower electrode. The associatedchamber door is then closed, and the upper electrode is lowered to thatprecise preselected gap that implements the particular plasma processbeing run. The intended reactants are then injected through the gasmanifold of the upper electrode, and radio frequency power is applied.Whereupon, plasma etching of each single wafer is continued until thelaser provides a signal indication that the proper end-point has beenachieved. Thereafter, the RF power is turned-off, the vacuum lock isopended, and the above-described process is repeated, but in reverseorder, for removing the wafer out of that plasma chamber and back intothe load and unload station. The wafer can then be moved into anotherplasma reactor for a subsequent process in a two or more step processingmode, or back into the cassette in a one-step processing mode.

The load and unload module, queuing station, and plural reactors areoperable in three basic modes, namely, where each reactor issimultaneously performing the same plasma reaction, where each plasmareactor is simultaneously performing two or more different plasmaprocesses, and where the plasma reactors are severally being operated toprovide multiple-step processing of single wafers before their returnback to the queuing station. In each case, the wafers are transferredand processed in a controlled vacuum environment such that atmosphericexposure and handling induced contamination are wholly eliminated.

FIG. 13-17 are scanning electron micrographs illustrating exemplarymicrostructures capable of being formed in a single-step process, andFIG. 18 is a scanning electron micrograph illustrating an exemplarymicrostructure capable of being fabricated in a double-step etchprocess. FIG. 13 shows generally at 260 polysilicon with an overlayedphotoresist 262 on the surface of the silicon dioxide layer 264 of thewafer. For exemplary low-resistivity (12-30 ohms) doped polysilicon,CCl₄ at 20 sccm and H_(e) at 30 sccm are applied to the plasma reactorat a pressure of 100 mt and a power of 30 watts. The etch occurs forapproximately 11/2 minutes. As shown in FIG. 14 doped polysilicon 265having a comparitively high resistivity (30-200 ohms per sq.) and havinga slopped profile mask is illustrated. For the illustratedmicrostructure, SF₆ at 50 sccm and freon 115 (C₂ CIF₅) at 50 sccn arecontrollably injected into a plasma reactor at 150 mt pressure and a 100watt power. After about 21/2 minutes, the illustrated doped polysiliconmicrostructure is fabricated.

Referring now to FIG. 15, generally designated at 266 is a SEMillustrating an exemplary trench etch. The photoresist is removed, and atrench generally designated 268 is formed in the silicon 272 byinjecting BCl₃ at 5 sccm and Cl₂ at 25 sccm into the plasma reactor at a100 mt chamber pressure and at 750 watts power for about 20 minutes.

Referring now to FIG. 16, refractory silcide, TaSi/poly, is illustratedgenerally at 274. The silicon dioxide surface 276 is overlayed with apolysilicon layer 278 upon which is overlayed the TaSi/poly 280 overwhich is the photoresist. The microstructure is fabricated by injectingCCl₄ at 20 sccm and He at 30 sccm into a plasma reactor maintained at achamber pressure of 80 mt and a radio frequency power of 300 watts forabout 31/2 minutes.

Referring now to FIG. 17, generally designated 282 is anothermicrostructure exemplary of the single-step structures capable of beingfabricated by the contamination-free and multiple-processing plasmareactor of the present invention. As illustrated, a photoresist 284 islayed over an aluminum and silicon layer 286 which is overlayed via aTiW layer 288 on the wafer surface. The illustrated structure wasfabricated by injecting BCl₃ at 50 sccm with Cl₂ at 15 sccm into theplasma reactor maintained at 125 mt chamber pressure and a 300 watt RFpower for about 21/2 to 31/2 minutes.

Referring now to FIG. 18, generally designated at 290 is a silicondioxide/poly/silicon dioxide/poly sandwich structure illustrating anexemplary two-step process. A poly layer designated poly 1 and an oxidelayer designed oxide are formed after etching with C₂ F₆ at 100 sccm ata 700 mt pressure and a 600 watt radio frequency power in a firstchamber. Thereafter, the upper poly 2 layer and the oxide and anoverlayed photoresist layer are formed by a separate step employing CCl₄at 20 sccm and He at 30 sccm in a second reaction chamber maintained ata 100 militore chamber pressure and a 600 watt radio frequency power.

With respect now to FIGS. 19-24, the processor control for waferthroughput is illustrated. In particular, FIG. 19 illustrates a statediagram for overall system operation. In the state 300, systeminitialization procedures are accomplished which take the system from aturn-on state through necessary warm-ups and start up proceedures.Transition to a subsequent state 302 occurs once the systeminitialization has been completed. State 302 exists until a cassette hasbeen placed into the cassette queue station and all door interlockswitches are activated. The transition from the determine ready state302 to a machine initialization state 304 occurs once these conditionshave been met and the operator initiates system operation through astart button, provided no other system interrupt signals or holddesignations have occurred and provided the user has not activated thediagnostic state 306 which is alternatively entered from the determineready state 302.

The diagnostic state 306 runs a set of diagnostics on the system shouldthat state be entered by the user. Otherwise, the machine initializationstate 304 accomplishes a final set of system power-ons, gas perge orother initialization steps which would not normally be entered in thesystem initialization state 300 for time and/or power considerations.

From the machine initialization state 304 a standby state 306 may beentered by operator designation through a standby button whicheffectively aborts the processing steps back to the determine readystate 302. Otherwise, from the machine initialization state 304, oncethe initialization functions have been completed, the system transitionsto a cassette pump down state 310 in which a vacuum is drawn from thewafer queuing station 14 placing it into the environment of thetransport arm and plural etch vessels. After pump down of the waferqueuing station 14, state 310 processing will normally transition to thestate 312 in which the wafers and the cassette at the queuing station 14are processed in sequence as illustrated in the subsequent figures.Alternatively, if in the determine ready state 302 the operator hadactivated a clear wafer instruction, processing would transition to aclear wafer state 314 in which, in liew of cassette processing, wafersare cleared from the system. In the case of each state 306, 308, and 314processing, after completion of their state functions, will return tothe determine ready state 302.

If the cassette processing state 312 is entered, the system processeseach wafer in the cassette according to a wafer command list enteredinto the system and described below. Once that cycle is complete,processing proceeds to a state 316 which vents the wafer queuing station14 and waits until removal of the cassette at which point the systemtransitions to state 300.

Should any error occur in normal system operation, as determined byprocessor error detection, processing from each of the states of FIG. 19will return to the system initialization state 300 to rerun the power-oninitialization functions.

The operation within the cassette process state 312 follows a flexibleprocesses control illustrated in the flow diagram of FIG. 20. Asillustrated there processing proceeds between state 320 labeled slots,state 322 labeled wafers, state 324 labeled wafer commands, and state326 labeled machine monitors. The processing of FIG. 20 is initiatedwhen the state 312 is entered with a cassette of unprocessed wafers, andstarts, and finishes, in state 320. State 320 initiates a wafer startcommand for each slot containing an unprocessed wafer using, forexample, a top to bottom priority scheme, or any other priority schemewhich may be programmed. From the state 320 for a selected slot, andcorresponding wafer, processing proceeds to the wafer state 322. Fromstate 322 the processing commands or specifications for each wafer areaccessed in a subsequent state 324, wafer commands. The wafer commandswill be programmed into the system corresponding to the desiredprocessing of each wafer, for example, one or more etches for adesignated time period or depth in a designated gas. The commands in thestate 324 are executed in sequence, and each command commences a set ofmachine control operations which occur in state 326, machine monitors.

At the completion of each wafer command, representing for example, asingle etch cycle for a wafer as described below, processing returns tothe wafer command state 324 to execute another wafer command. After allwafer commands have been executed for a particular wafer, processingreturns to the state 322 and from thence to state 320 thereby sequencingthrough the wafers and the cassette slots.

Processing within the machine control state 326 is in accordance withthe wafer transport algorithms of FIGS. 21, 22 and 23 and the internalchamber or vessel processing algorithm of FIG. 24. In each case whereprocessing halts for receipt of system instructions to proceed,processor state evaluation checks for existence conditions necessary forthe unit to proceed to the next step.

With particular regard to FIG. 21 illustrates processing for moving awafer from one chamber or vessel to another, in accordance with wafercommands specifying multiple chamber or vessel processing. As shownthere processing commences at initialization state 330. Subsequent state332 directs the transport arm wafer support table from one chamber orvessel to the desired chamber or vessel wherein the wafer to be moved islocated. Once that positioning is accomplished a subsequent state 334activates the valve and arm mechanisms in a transition to a state 336.In state 336 the system repositions the transport arm wafer supporttable to the destination chamber or vessel and transitions to a state338 which, when it receives control signals, activates the arm mechanismand valving on the applicable chamber to place the wafer in thatparticular chamber in the transition to a state 340. When state 340 isreached, the wafer relocation function is complete and processingreturns to the next wafer command in state 324.

FIG. 22 illustrates the processing wherein a wafer is moved from achamber or etch vessel to a slot of the cassette. From an initializationstate 350 processing transitions to a state 352 which awaits thedirection of the transport arm wafer support table to the desiredchamber having the wafer to be returned to the cassette. Once the properpositioning is accomplished, the transition from state 352 to state 354sends a request to the command list asking to be instructed to removethe wafer from the chamber. When that instruction is received in state354, the transition to state 356 executes the machine instruction toopen the valves and move the transport arm to pick up the wafer in thechamber and extract it from the chamber or vessel and in addition torequest from the wafer command list the instructions to move to thecassette. When those instructions are executed and the arm is positionedto apply a wafer to the cassette, the system transitions to state 358and sends a request to the wafer processing list for instructions toplace the wafer into the cassette and identified slot. When thatinformation is received the transition to the done state 360 executesthe wafer insertion into the cassettes slot and returns processing backto the algorithm of FIG. 20.

FIG. 23 illustrates the algorithm for transferring a wafer from thecassette to a designated chamber in accordance with instructions in thewafer command list. From an initialize state 370, processing transitionsto a state 372 in which the request is sent to the command list forinstructions to position the arm to the cassette and such armmanipulation is executed. When the arm is appropriately positioned instate 372, the system transitions to state 374 in which a request forthe instructions to extract a wafer from the cassette is sent. The state374 has two possible outcomes, in the first represented by branch 376, awafer is not found in the slot in which the system has been instructedto retrieve it by the transport arm. In this case the system transitionsto a done state 378 indicating that the algorithm of FIG. 23 hasprogressed as far as it can, albeit in an abort condition. In the otherpossible outcome of state 374, the wafer is found and the systemtransitions from state 374 to state 380 in which instructions arereceived from the wafer processing list to position the transport armsupport table at the destination chamber or vessel. When, in state 380,that destination chamber is reached, the system transitions to a state382 in which the system requests and receives instructions from thecommand list (if the chamber is ready) to insert that wafer into thechamber. In the transition from state 382 to the completed state 378,the mechanisms of the arm and the chamber valving are activated in orderto install the wafer into the chamber.

FIG. 24 illustrates the processing of the system for accomplishing waferetching within a chamber to which the system has allocated a wafer fromthe cassette at the queuing station.

The processing of FIG. 24 is initiated by a start command obtained fromthe command list which initiates a state 390. The state 390 loopsthrough an error recognition state 392 to a start command wait step 394if the start command is determined to have incorrect signature.Otherwise, processing from a state 390 proceeds to a state 392 in whichthe valve to the chamber is sealed and the electrode spacing set to theetch condition. A subsequent step 394 waits for confirmation signalsfrom microswitches indicating proper gate closure and electrodepositioning. Subsequently a state 396 commences the flow of a gas,selected from the wafer command list, for the desired processing andwaits for a steady state gas condition, based on time or other factors,to occur. Subsequently a transition to a state 398 activates the RFplasma generation between the electrodes used for plasma etching withinthe gas and wafer processing by gas vapor etch continues until aparameter indicating complete processing is obtained. Such a parametermay be a function of time, detected etch depth, or other factors. Oncewafer processing is indicated as complete, the transition from state 398to state 400 deactivates the RF and in state 400 the gas environment inthe chamber is evacuated so that, in subsequent state 402, theelectrodes can be respaced for wafer removal, and the gate or chamberdoors opened to the environment of the transport arm without fear ofleaking reactor gas into that environment. State 402 transitions tostate 404 in which the system awaits confirmation by microswitchactivation of proper electrode spacing and opening and transitions tostate 394 in which system processing returns to the flexible processcontrol of FIG. 20.

Many modifications of the presently disclosed invention will becomeapparent to those skilled in the art without departing from the scope ofthe appended claims.

What is claimed is:
 1. A multiple-processing and contamination-freeplasma etching system, comprising:plural, single-wafer plasma etchingvessels each having an ingress and egress defining port that are arrayedabout a predetermined spacial locus in such a way that the several portsthereof are accessible form a single location spaced from the severalports; a wafer queuing station spaced with the plural vessels along thesame predetermined spacial locus defining a wafer access port accessiblefrom said single location; plural valve means individually coupled tocorresponding ones of said plural, single-wafer plasma etching vesselingress and egress ports and to said wafer queuing station wafer accessport; single-wafer transfer means disposed at said single location andcooperative with corresponding ones of said plural valve means formoving wafers from and to said wafer access port of said queuing stationfrom and to selected ones of said single-wafer plasma etching vesselsthrough the associated one of said ingress and egress ports thereof; andprocessor means for controlling said vessels, said transfer means andsaid valve means to provide selectable single or multistep processing ofwafers in said queuing station in one or more of said etching vessels.2. The system of claim 1, wherein said predetermined spacial locus is aclosed locus, and wherein said single location coincides with thegeometric center of said closed locus.
 3. The system of claim 1, whereinsaid wafer queuing station includes a cassette and an indexing elevatormechanism for moving said cassette in the vertical direction.
 4. Thesystem of claim 1, wherein each of said plural plasma etching vesselsinclude walls defining a plasma chamber.
 5. The system of claim 4,wherein each of said plural plasma etching vessels further include firstand second electrodes, and means for mounting said first and said secondelectrodes to said walls for relative electrode motion.
 6. The system ofclaim 5, wherein each of said plural plasma etching vessels furtherinclude a pedestal inset into one of said electrodes, and means formounting said pedestal for vertical motion relative to said one of saidelectrodes.
 7. The system of claim 5, wherein each of said plural plasmaetching vessels further include means for cooling/heating said first andsaid second electrodes thereof.
 8. The system of claim 1, wherein saidwafer transfer means includes a wafer receiving arm, and means mountedto the arm for picking-up single wafers by contacting their peripheryand in such a way that no contact is made of the front surface of thewafer.
 9. The system of claim 2, wherein said wafer transfer meansincludes an R, TT moveable wafer receiving arm having means forpicking-up single wafers disposed on said arm by contacting theirperiphery and in such a way that no contact is made of the front surfaceof the wafers.
 10. The system of claim 9, wherein said R, TT moveablewafer receiving arm assembly includes a base member platform and meansfor rotating said base member platform in TT about an axis; a paddle;and means for mounting said paddle for sliding motion in R relative tosaid base member platform.
 11. The system of claim 10, wherein saidpaddle includes a wafer supporting first portion, a wafer edge engagingsecond portion, and means for mounting said second portion for slidingmotion relative to said first portion.
 12. The system of claim 11,wherein said first portion of said paddle has an upstanding abutment onan edge thereof and wherein said wafer edge engaging second portionincludes a slide having a bumper that cooperates with said upstandingabutment of said first portion to engage the periphery of a single waferdisposed therebetween.
 13. The system of claim 12, wherein said paddlefurther includes means for resiliently urging said bumper towards saidabutment.
 14. The system of claim 13, further including means forsensing whether or not the wafer is seated on the platform.
 15. Thesystem of claim 14, wherein said sensing means includescontact-responsive switches mounted to the platform.
 16. The system ofclaim 1, wherein each of the plural single-wafer plasma etching vesselsincludes a low-frequency plasma discharge producing source.
 17. Thesystem of claim 1, wherein each of the plural single-wafer plasmaetching vessels includes a high-frequency plasma discharge producingsource.
 18. The system of claim 1, wherein each of the pluralsingle-wafer plasma etching vessels includes a microwave-frequencyplasma discharge producing source.
 19. The system of claim 16, whereinthe low-frequency plasmas are produced at frequencies approximately of 4to 450 khz.
 20. The system of claim 17, wherein the high-frequencyplasmas are produced at frequencies approximately of 1 to 50 mhz. 21.The system of claim 18, wherein the microwave-frequency plasmas areproduced at frequencies approximately 1 to 4 mhz.
 22. The system ofclaim 5, wherein said electrodes are in a diode configuration.
 23. Thesystem of claim 5 wherein said electrodes are in a triode configuration.24. The system of claim 5, further including means for magneticallyenhancing said electrodes.
 25. A system for providing semiconductorwafer etch processing of a plurality of semiconductor wafers containedin a cassette in conjunction with a plurality of wafer etch chamberscomprising:an array of wafer stations comprising:at least one wafercassette queuing station adapted for containing a plurality of wafers inindividual slots of a wafer containment cassette; a plurality of waferetch vessels; means for providing gated entrance to said wafer etchvessels to provide in a first state sealed containment of an environmentwithin each of said vessels and in a second state access to the vesselinterior; means for transporting wafers between selected slots in acassette at said queuing station and the interior of selected plasmaetched vessels via said gated entrance means in said second state;processor means for sequencing wafers between associated slot positionsin a cassette of said queuing stations and one or more of said plasmaetch vessels in accordance with plasma processing commands associatedwith each wafer.